SMS (short message service) comprises a method of sending messages to users of mobile devices and other computer devices supporting the protocol. In order to achieve interoperability between wireless carriers, SMS is sent via a well-defined, standards-based protocol. This protocol is comprised of multiple predefined parameters, each with a predefined octet length for its relevant data. SMS are sent through SMS centers where they are stored before being forwarded to their ultimate destination.
MMS (multimedia message service) comprises a method of sending messages much larger than SMS which include encoded attachments such as image, video and audio among others. MMS also uses a well-defined standards-based protocol. MMS are sent from mobile devices to a store and forward server which then uses SMS to notify handsets of waiting attachments which are stored separately and retrieved via Hypertext Transfer Protocol (HTTP).